The present invention generally relates to fluid filtration apparatus and, in a preferred embodiment thereof, more particularly relates to an oil filter assembly having uniquely integrated full flow and bypass flow portions.
In its broadest sense, a fluid is a substance (such as a liquid or a gas) capable of flowing within a defined system and/or conforming to the outline of a container in which it is stored. A system or other device within which one or more fluids flows along an expected fluid flow path may include a fluid filter. Within the system or device, the fluid filter is oftentimes positioned along the expected fluid flow path such that the fluid will flow through the filter. For example, fluid filters are used in various automotive vehicle engine applications to remove contaminants from fluids flowing within the engine, for example, the engine oil currently used to lubricate bearings and reduce friction in automotive vehicle engines. Of course, it should be clearly understood that there are a wide variety of other applications other than those specific applications set forth herein which may benefit from incorporation of one or more fluid filters along a fluid flow path thereof. Accordingly, it is contemplated that such applications may include (but are not necessarily limited to) vehicle engine applications other than those specifically recited herein, non-engine vehicle applications, for example, fuel delivery systems, and non vehicle engine applications, for example, turbine engine applications, as well as any other applications not specifically recited herein but characterized by a fluid flow within a defined area.
In the aforementioned automotive vehicle engine application, lubricating oil is circulated through the engine and carries contaminants such as metal particles, carbon particles and dirt which may cause harm to the engine. In order to effectively lubricate the engine, engine oil is passed through a filter to remove the contaminants before the oil is recirculated into the engine. The typical oil filter is attached to an internal combustion engine at an oil filter receptacle portion thereof. Engine oil passes through a discharge opening in the oil filter receptacle, into a fluid filter, and then into the engine lubrication system through an oil inlet pipe. A filter element in the fluid filter removes contaminants from the oil before it reenters the engine through the oil inlet pipe. Oil filters for gasoline and diesel engines have traditionally been of the xe2x80x9cfull flowxe2x80x9d type in which engine-generated oil pressure is utilized to flow all of the oil discharged from the engine through a filtration element in the overall filter structure before returning the oil to the engine. While this full flow type of oil filter structure is widely used, and generally suited for its intended purpose, it is subject to a variety of well known problems, limitations and disadvantages. For example, this type of full flow filtration structure is normally suited for removal of relatively large size particulate matterxe2x80x94namely, particles of a 40 micron size and larger. Smaller contaminants, such as soot particles generated by diesel engines, simply pass through the filter element and are permitted to be returned to the engine. Another disadvantage of conventional full flow oil filters is that since all of the oil discharged from the engine is flowed through the filtration element, such element has a relatively limited duty cycle before it becomes clogged and must be replaced (if the filtration element is of a disposable type) or cleaned (if the filtration element is of a cleanable, reuseable type).
The useful life of a full flow filter assembly may be extended by increasing the effective area of its filtration element, such as by providing the element with a pleated configuration. However, this adds considerably to the cost of the element, makes it a great deal thicker, and substantially increases the difficulty in cleaning the element if it is of the reuseable type.
Another approach to extending the duty cycle of a full flow type filter assembly is illustrated and described in U.S. Pat. No. 5,569,373 to Smith et al. which is hereby incorporated by reference herein as if reproduced in its entirety. In the illustrated full flow type filter assembly therein, oil forced from the engine into an outer tubular canister portion of the filter assembly is directed through axially and circumferentially angled inlet openings disposed radially outwardly of a tubular full flow filtration element coaxially disposed within the canister. The angulated orientation of these inlet openings causes the oil discharged into the canister to swirl in a vortex pattern outwardly around the filtration element, with the result that particulate matter is forced outwardly away from the outer side surface of the filtration element.
Due to this vortex-created centrifuge action imparted to the incoming particulate-bearing oil, partially purified oil is forced through the filtration element and then returned via the interior of the element to the engine. Particulate matter forced outwardly toward the inner side surface of the canister, and thus prevented from flowing inwardly through the full flow filter element, falls by gravity into a lower contaminant chamber of the filter assembly.
While the duty cycle of the vortex-based full flow oil filter assembly illustrated and described in U.S. Pat. No. 5,569,373 is substantially increased compared to full flow oil filter assemblies of more traditional constructions, the filter assembly is still relatively ineffective in filtering out sub-40 micron size particles such as soot particles created in abundance by diesel engines. These small contaminant particles, for the most part, simply pass through the filter element and are returned to the engine.
One conventional method of solving this problem of being unable to effectively filter out small (i.e., sub-40 micron size) contaminant particles with a full flow filter is to augment the full flow filter with a filtration structure commonly referred to as a bypass filter structure. This bypass filter structure has a filtration element sized to trap the small contaminant particles that the full flow filtration assembly cannot separate from the oil, and is connected in parallel with the full flow assembly. The bypass filter structure is mounted remote from the full flow filtration structure and is connected thereto by appropriate hoses. Oil discharged from the engine during operation thereof is routed separately to the full flow and bypass flow filtration structures, with only a small portion of the discharged oil (i.e., less than ten percent in most cases) being flowed through the bypass filtration structure. In this manner, large and small contaminant particulates are separately handled.
As conventionally practiced, this dual filtration structure approach has a variety of problems, limitations and disadvantages. For example, it substantially adds to the cost and complexity of the overall filtration system and makes it more difficult and time consuming to maintain. Additionally, the necessity of using hoses connected to the filtration apparatus substantially increases the possibility that leaks will develop in the system due to, for example, vibration stresses being imposed for long periods on the hoses and their fittings. Furthermore, since two separate filtration systems must be employed under this scheme, more space must be dedicated to the filtration system.
From the foregoing it can readily be seen that a need exists for fluid filtration apparatus that provides the benefits of both full flow and bypass flow types of filtration structures while at the same time eliminating or at least substantially reducing the above-mentioned problems, limitations and disadvantages commonly associated with auxiliary bypass flow filtration structures. It is to this need that the present invention is primarily directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a specially designed fluid filtration apparatus, representatively an oil filter assembly, is provided. From a broad perspective, the fluid filtration apparatus comprises a housing structure having an internal flow path through which a fluid to be filtered may be flowed; and full flow and bypass filtration structures operably interposed in the internal flow path, with the full flow and bypass filtration structures being disposed in series within the internal flow path, preferably with the full flow filtration structure being disposed upstream of the bypass filtration structure. Representatively, the full flow and bypass filtration structures respectively have generally tubular and cylindrical configurations, with the bypass filtration structure being coaxially nested within the full flow filtration structure.
In a preferred embodiment of the fluid filtration apparatus, the housing structure has a generally tubular configuration, a fluid inlet area and a fluid outlet area. The full flow filtration structure is defined by a generally tubular full flow fluid filter element coaxially and removably supported within the housing structure and defining with an interior surface portion thereof an annular outer flow area communicated with the fluid inlet area. The generally cylindrical bypass fluid filtration structure is coaxially supported within the full flow fluid filter element and defines therewith an inner annular flow area, the bypass fluid filtration structure having an outlet portion communicated with the fluid outlet area of the housing structure.
The fluid filtration apparatus is operative in response to forced flow of a pressurized fluid to be filtered inwardly through the fluid inlet area of the housing structure to flow the fluid sequentially through the annular outer flow area, through the full flow filter element, through the inner annular flow area, through the bypass fluid filtration structure, outwardly through the outlet portion of the bypass fluid filtration structure, and outwardly through the fluid outlet area of the housing structure.
Preferably, the fluid inlet area of the housing structure is configured in a manner such that pressurized fluid forced inwardly therethrough traverses the outer annular flow area in a whirling flow pattern centered about the full flow fluid filter element.
According to a feature of the invention, the bypass fluid filtration structure preferably includes a generally tubular bypass portion in which the outlet portion is formed, and a generally tubular filtering portion communicating with the outlet portion. The outlet portion, in response to forced fluid flow therethrough, is operative to create a lowered pressure area serving to draw fluid through the filtering portion and into the bypass portion for discharge therefrom through the fluid outlet area of the housing structure. Preferably, the outlet portion is operative to impart to fluid being discharged therefrom a swirling flow pattern.
In a preferred embodiment thereof, the bypass portion has a side wall surface portion and an outlet end surface. The outlet portion includes a circumferentially spaced series of discharge passages extending inwardly through the side wall surface portion, opening outwardly through the outlet end surface and being axially and circumferentially angled relative to the axis of the bypass portion. The generally tubular filtering portion preferably includes a perforated flow tube member having a first longitudinal portion removably and coaxially received in the bypass portion, and a second longitudinal portion, and a tubular bypass fluid filter element removably and coaxially telescoped onto the second longitudinal portion of the perforated flow tube. In further aspects of this embodiment, the tubular bypass fluid filter element is preferably a cleanable and reuseable filter element or, alternately, a disposable filter element. Similarly, in further aspects of this embodiment, the full flow fluid filter element is preferably a cleanable and reuseable filter element or, alternately, a disposable filter element.
While the fluid filtration apparatus is representatively embodied in an oil filter assembly, the principles of the present invention are in no manner limited to this particular filtration structure, and can alternatively be utilized to advantage in a variety of other filtration applications in which a variety of other types of fluids, including, but not necessarily limited to, liquids and gases, are to be filtered.